If you don't want to use your mouse, the following keyboard shortcuts work both in normal view and in fullscreen:

ctrl-0: full page

ctrl-1: zoom to 100%

ctrl-2: page width

for more control you can use
ctrl-plus and ctrl-minus to zoom in and out as you want (they do the same as ctrl+mousewheel).

And a last useful shortcut: ctrl-h
This goes to 'Reading mode', hiding most of the taskbars at the top and the left. It's not the same as fullscreen mode, but is sometimes useful if you want to maximize the reading area but still have your Windows taskbar (and Acrobat's menu) available.